1. Field of the Invention
The invention relates to a method for determining the set position of a motor-driven adjustment part of a motor vehicle by means of a Hall sensor, which is arranged in a magnetic field rotated as a result of a motor rotation, whereby the drive of the adjustment part is activated for a specified number of approaches of the adjustment part toward an end position, whereby a counter is changed by a count value upon each approach of the adjustment part toward the end position, and whereby a standardization run to the end position is carried out when the specified number of approaches is reached. It refers further to an adjustment system operating according to this method.
2. Description of the Background Art
A plurality of adjustment devices or adjustment parts (adjustment elements), driven by electric motors, are typically present in a modern motor vehicle. These are, for example, an electric window lift or a sunroof. During a setting process of such an adjustment part a desired end position is to be reached precisely, to which end the set position of the adjustment element must be known accurately. Moreover, it is also often necessary to know the current set position or the parameters that can be derived therefrom, such as the setting speed or the traveled adjustment path, for the reliable detection of a case of pinching.
For example, DE 199 16 400 C1, which corresponds to U.S. Pat. No. 6,225,770, and which is incorporated herein by reference, discloses the provision of a position and rotation sensor for the most precise detection possible of the set position of a window pane. It includes two Hall sensors offset at a distance or angle from one another or a Hall sensor (Hall IC) having two Hall probes (sensitive surfaces) and a multipole, for example, two- or four-pole ring magnet, which is arranged on the drive shaft of the electric motor. The Hall sensor detects a change in the magnetic field due to a rotation of the ring magnet, fixedly connected to the drive shaft, and generates counting pulses therefrom. These are evaluated together with information on the rotation direction of the ring magnet and thereby of the electric motor, by counting the counting pulses upward or downward depending on the rotation direction of the drive and thus indicating the respective position of the window pane.
DE 10 2006 043 839 A1 discloses a conversion of magnetic field changes, occurring at Hall probes or Hall sensors, of a comparator circuit with hysteresis (Schmitt trigger circuit) into two binary pulse trains, offset, for example, by 90° to one another. An upper switching threshold and a lower switching threshold are provided in such a comparator circuit with hysteresis. The motor or drive speed and thereby the position of the adjustment part and the rotation direction of the electric motor or rotary drive can be determined by counting the pulses per unit time by a comparison of the two pulse trains.
In adjustment systems with two end positions (open and closed), such as particularly in the case of a window lift drive, first as part of a first learning or standardization cycle, at least one of the end positions is directly approached and in this position the count value of a counter is set to a specific value, particularly to zero. During the movement toward the other end position due to an activation of the drive or electric motor in the opposite direction, the Hall sensor generates a number of counting pulses, which, for example, increment a position counter, whereby when the other end position is reached the current counter state is assigned to this end position and, for example, is stored. Thereby, each position of the driven adjustment part along the adjustment path between the two end positions is assigned a count value of the position counter. During the subsequent movements toward this end position, particularly the closed position (approach cycles), the drive is stopped shortly before reaching the standardized count value during normal operation in order to perform so-called soft starts of the adjustment element in the end stop, also designated as a capture region or seal entry, to increase the lifetime solely due to the inertia of the system.
To take into account changes in the adjustment system that occur during proper use, e.g., the end position, and to postadjust the adjustment system, DE 195 27 456 B4, which corresponds to U.S. Pat. No. 5,777,446, discloses the movement toward the end position in a standardization run without a soft start after a specified number of approach cycles and the resetting of the counter for the purpose of standardization to a specific value, for example, again to zero. In this way, a fixed number of approaches is specified after which a standardization run occurs in each case.
DE 198 38 293 A1, which corresponds to U.S. Pat. No. 6,346,787, discloses, moreover, instead of a fixedly specified number of approach cycles, to design the number of cycles as variable and to this end after each standardization run to generate a random number for the subsequent approach cycles, after which the next standardization run is to occur. The wear of the system is said to be reduced and the lifetime increased by generating the random number, which is decremented with each approach cycle of the adjustment part, to be positioned, up to the specified count value, which triggers a standardization run.